Sediment cores were taken in the coastal area of Ba Lat estuary (Red River), in the Xuan Thuy national park. Each core was cut into slices of 4 cm in thickness, numbered from top to bottom and then analyzing for radionuclides (226Ra, 137Cs and 210Pb). Computational dating models were used to determine the age and sedimentation rate for each sediment core. This report presents the results of applying computational models to the sediment core BL13 that could provide a general methodology for determining the age and the sedimentation rate of the sediment cores taken in the coastal area of Ba Lat estuary. Results show that Constant rate of supply (CRS) model is probably the best model for determining the sedimentation rate. For the sediment core BL13, the use of the Composite model by adjusting the results of the CRS model in combination with the time marker of August 1971 (the time of the historical flood event on the Red River) seems to give the most reasonable results. The average sedimentation rate at the BL13 site before 1960 was about 0.5 cm/year. The rate had increased significantly from 1960, up to the highest value of 1.5 cm year-1 in the 1970s and then decreased to about 1.0 to 1.2 cm/year from the 1980s to the present. The change in the sedimentation rate could be caused by the main flow changes and large floods of the Red River from 1960 to 1980.

In this study, ARGOS software was used to simulate the atmospheric radioactive emissions from Fangchenggang nuclear power plant to Viet Nam. The simulated cases are hypothetical accidents with hypothetical source terms equivalent to level 6 of the International Nuclear and radiological Event Scale (INES). The results show the possibility of using ARGOS in simulating atmospheric dispersion, assessing radiation dose to humans from the Fangchenggang nuclear power plant accident to Viet Nam in some accident situations. Furthermore, the obtained results contribute to forecasting and supporting emergency response when an accident occurs in nuclear power plants.

In this study, we have tested the possibility of parallel measurement of radon (222Rn) and thoron (220Rn or Tn) by alpha track detectors at the extraction and processing of black sands that contains high content of Zircon and Monazite minerals in a coastal area of the Ha Tinh province. A pair of cylindrical cups RADUET, designed to separately measure Rn and Tn with CR-39 detectors (Radosys Company Ltd – Hungary), were used for the test. The results showed that concentrations of indoor Rn and Tn in the black sand extraction area are not high (28 ± 6 Bq/m3 for Rn, 14 ± 5 Bq/m3 for Tn). The Rn and Tn concentrations in the indoor air of the titanium processing plant are 34 ± 6 Bq/m3 for Rn, 58 ± 11 Bq/m3 for Tn, and are higher than those concentrations in the residential houses outside the plant (20 ± 4 Bq/m3 for Rn, 16 ± 8 Bq/m3 for Tn) but still comparable to the average concentrations of indoor Rn and Tn reported by the UNSCEAR 2006. At Zircon processing plant, indoor Rn concentrations are similar to those in the titanium processing plant but Tn concentrations in the houses for separating Rutile and Zircon are very high. Indoor Tn concentration is especially high in the house for separating Zircon where it could reach 2931 Bq/m3, hundred times higher than that in the surrounding residential houses and that of the world average published by UNSCEAR 2006.

Calculating gamma radiation dose rate from online real-time environmental gamma spectrum using NaI(Tl) detector has been developed into a software named RADAPROC V.1 in the Center for Operating the National Network of Environmental Radiation Monitoring And Warning (CONNERMAW). Currently, hundreds of online gamma spectra per day from online monitoring stations are processed to calculate the total ambient dose equivalent rate and the ambient dose equivalent rate of typical natural radioactive isotopes such as K-40, Bi-214, Tl-208 according to the method of using the function G(E) and the photo-peak area method. The calculated results have been compared with the results of calculating the dose rate from the specific activity of radioactive isotopes in soil samples collected at the same monitoring location and analyzed in the laboratory. The difference between the methods is less than 25%. The ambient dose equivalent rates of typical natural radioactive isotopes are a bit higher than those calculated with SARA-NMC software. The software will be improved shortly for better results.